The North was bleeding the South dry through use of export taxs.
The North used slavery as an excuse to wage war with the South and to keep the British from helping the South.
If there had been no slaves in the South at that time. Then the North would have found or made up another or excuse to wage war with the South.
By the way, there were two NORTHERN Slave States before, during and after the Civil War/War between the States. These two NORTHERN Slave States did not become Free States until some time in the 1880's. Long after the Civil War/War between the States was over.
There was no export tax. Duties or taxes on exports are unconstitutional.
By the way, there were two NORTHERN Slave States before, during and after the Civil War/War between the States
By the way, there were four NORTHERN slave states. Five when West Virginia was admitted.